1. Field of the Invention
The present invention relates to cabling systems, and more particularly to connectors that may be used in systems including elements sensitive to static electric discharges.
2. Discussion of Related Art
Unshielded twisted pair (UTP) cables include several, for example, four, twisted pairs of conductors surrounded by a dielectric insulation. These cables are often used in high speed networks, for example, a local area network (LAN), to connect equipment, such as computers and/or telephones.
Unshielded twisted pair cables that are left unconnected or temporarily unused in a cabling system tend to act as capacitors and accumulate charge. The cables can often build up a very high charge, for example, up to 15 kV, which can cause serious damage to network equipment if the cable is connected before the accumulated charge is dissipated.
The cables can accumulate charge in a number of different ways. For example, if a cable is dragged along the floor, positive charges are created at the surface of the cable. The positive charges on the surface tend to attract negative charges on the twisted pairs, which causes charge separation leading to positive charges being present at the ends of the cable. If the cable is plugged into a directly or capacitively grounded connector, this build up of charge may cause arcing which could damage the cable or equipment to which the cable is connected. In another example, a cable that is placed in a strong electrostatic field and left there for some time will also accumulate charge on its surface. This charge tends to polarize the twisted pairs and cause some migration of the charge inside the dielectric insulation of the cable. After the cable is removed from the external electrostatic field, the charge remains, inducing a positive charge at the ends of the cable, as described above. Unconnected cables that are left in a dry environment can also accumulate charge from dust or other particles settling on the cable insulation.
When a cable has accumulated a large charge between its twisted pairs and the surroundings, this differential charge will cause charge carriers to migrate into the dielectric insulation. If the twisted pairs are grounded for a few seconds, the charge on the twisted pairs themselves, which can move quickly through the copper, will be neutralized. However, the charge carriers inside the dielectric insulation will not be removed. Thus, after removing the ground connection, the charges in the insulation will again cause a charge separation on the twisted pairs, leading to a potential difference between ground and the end of the twisted pairs. This potential difference may still damage network equipment when the cable is connected. For this an other reasons, providing shielded connector jacks in the cabling system will not effectively discharge the cables. Shielded jacks and electronic components on networking equipment are designed to dissipate charge build-ups according to the xe2x80x9cHuman body model,xe2x80x9d i.e., the cable has accumulated an amount of static charge similar to that accumulated by a person, and having a similar characteristic. The static charge accumulated by unconnected UTP cables is often far greater than the xe2x80x9cHuman body modelxe2x80x9d and has a different discharge characteristic, and thus shielded jacks and electronic components on networking equipment are not an effective solution.
According to one embodiment, an electrical jack may include a housing having an opening defined therein through which a mating plug is received, a grounding strip and at least one elastically deformable signal contact residing within the housing. As the mating plug is received, the elastically deformable signal contact may move from a position in contact with the grounding strip to a position not in contact with the grounding strip, thereby grounding any electrostatic charges present in the mating plug.
According to another embodiment, an electrical connector panel comprises a housing and a plurality of connector jacks disposed in the housing. Each jack includes a plurality of spring contacts and the plurality of jacks is adapted to mate with a corresponding plurality of connector plugs. The connector panel further includes a grounding strip, coupled to a housing ground terminal, at least a portion of the grounding strip being disposed in a rear of the panel such that the plurality of spring contacts of each of the plurality of connector jacks are in contact with the grounding strip when in a first position, and wherein the plurality of spring contacts of one of the plurality of connector jacks move to a second position, not in contact with the grounding strip, when a connector plug is received by the connector jack.
According to one example, the grounding strip of either of the above embodiments may comprise metal or conductive plastic, or may include a dielectric with electrical circuitry disposed thereon.
Another embodiment includes a cabling system comprising at least one electrical cable terminated in a connector plug and a connector panel including at least one electrical jack adapted to receive and mate with the connector plug of the electrical cable, the electrical jack including a plurality of spring contacts movable between a first position and a second position. A grounding strip is disposed in the connector panel such that the plurality of spring contacts of the electrical jack are in contact with the grounding strip when in the first position, and the grounding strip is coupled to a chassis ground terminal. The cabling system further comprises network equipment coupled to the connector panel, and terminal equipment coupled to the connector panel by the at least one electrical cable. The plurality of spring contacts of the electrical jack are moved into the second position when the connector plug is received by the electrical jack, and the plurality of spring contacts are not in contact with the grounding strip when in the second position.
According to yet another embodiment, a method of discharging an unshielded twisted pair cable includes steps of securing a grounding strip in a housing of an electrical jack having a plurality of movable signal contacts and an opening adapted to receive a mating connector plug, such that the movable signal contacts are in contact with the grounding strip when in a first position, inserting the mating connector plug that terminates the unshielded twisted pair cable into the opening, and causing, by said inserting, the movable signal contacts to elastically deform to a second position not in contact with the grounding strip, thereby grounding any electrostatic charges present in the mating connector plug.